1. Field of the Invention
The present invention relates to a tilt sensor for detecting the tilting of a device such as a digital still camera or a mobile phone, for example.
2. Background of the Art
FIGS. 12 and 13 illustrate an example of conventional tilt sensor (see JP-A-2007-139643). The illustrated tilt sensor X includes a substrate 91, a case 92, a cover 93, a pair of light receiving elements 94A and 94B, a light emitting element 95 and a cylindrical rolling member 96. The light receiving elements 94A, 94B and the light emitting element 95 are mounted on the obverse surface of the substrate 91 and enclosed by the case 92. The case 92 and the cover 93 define a space 92a, into which the light emitting element 95 emits light. Then, the light may be reflected several times by the inner wall surface of the case 92 until it reaches the light receiving elements 94A and 94B. The rolling member 96 is arranged to roll within the space 92a. The substrate 91 is formed, at its reverse surface, with terminals to be used for the surface mounting of the tilt sensor to e.g. a circuit board.
FIG. 13 illustrates the state in which the tilt sensor X is held in an upright position, and the rolling member 96 is settled at the lowermost position due to gravity. In this position, the rolling member 96 conceals the light emitting element 95, blocking the light emitted from the light emitting element 95. Thus, no light from the element 95 reaches the left and right light receiving elements 94A, 94B.
When the tilt sensor X is tilted to the left (i.e., turned counterclockwise in FIG. 13), the rolling member 96 will move in the space 92a and go to a position at which the rolling member 96 conceals the left light receiving member 94A. In this state, the light emitted from the light emitting element 95 is received by the right light receiving element 94B, but not by the left light receiving element 94B. Likewise, when the tilt sensor X is tilted to the right from the upright position (shown in FIG. 13), the rolling member 96 will conceal the right light receiving member 94B, and the light from the light emitting element 95 is received only by the left light receiving element 94A.
The tilt sensor X may be incorporated in a mobile phone provided with a display unit, through which the user can view visual information. With such a mobile phone, it is possible to make arrangements for adjusting the orientation of the displayed images, based on the tilt detection by the tilt sensor X. Thus, the use can view the corrected images in the proper position even when the mobile phone is tilted by the user.
The conventional tilt sensor X may still remain to be improved in the following respect. As seen from FIG. 12, the space 92a accommodating the rolling member 96 is stacked on the space accommodating the light receiving elements 94A, 94B and the light emitting element 95. Accordingly, the overall thickness of the tilt sensor X is inevitably much greater than a total of the height of the light receiving elements 94A, 94B (or the light emitting element 95) and the length of the rolling member 96. This is a hindrance to provide a compact tilt sensor.